Process of using hydrogenated solvents for dewaxing oils



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1933- J. v. STARR v 2,126,055

PROCESS OF USING HYDROGENATED SOLVENTS FOR DEWAXING OILS I Filed Nov. 1, 1934 7 fXC/r'A/VG'ER #54752 /149 Ail/YER FIL r52 2 C'HILLER H CONZEA/SER FRAC 770/044 772w;

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Patented Aug. 9, 1938 PATENT OFFICE PROCESS OF USING HYD.ROGJENA'IED SOL:- VENTS FOR D'EWAXING OILS John V. Starr, Cranford, N. J assignor to Standard Oil Development Company, a corporation of Delaware Application November 1, 1934, Serial No. 750,939

6 Claims.

The present invention relates to a process of dewaxing wax-containing oils, especially various lubricating oils and cylinder stocks of petroleum origin, or recovery of waxes of low oil content from crude wax bearing material, e. g. ozokerite, etc., and will be fully understood from the following description when read in conjunction with the drawing, the sole figure of which is a diagrammatic side elevation, partly in section, of an apparatus appropriate for carrying out the invention.

Various wax containing distillates or residual oils, hydrogenated oils, etc., are dewaxed, according to the present invention, by means of a hydrogenated solvent or a solvent mixture, one component of which is a wax precipitant and the other component is a hydrogenated solvent produced by vapor phase destructive hydrogenation of various petroleum distillates such as kerosene, gas oil, etc., and especially of extracts obtained in the treatment of petroleum naphtha, or refined oil stock or gas oil with a selective solvent, such as triphenyl phosphate, tri-ortho-cresyl phosphate, aniline, furfural, liquid sulfur dioxide, etc. Acetone, lower aliphatic alcohols, such as isopropyl alcohol, various aliphatic ketones, such as methyl-ethyl ketone; alkyl acetates, such as normal or secondary butyl acetate, organic acids such as acetic acid, etc., may be cited as examples of wax precipitant. The other component of the dewaxing mixture, namely, the hydrogenated solvent, has the property of maintaining the precipitant and the oily constituents in solution at low temperatures.

The hydrogenated solvents are obtained by destructive vapor phase hydrogenation of extracts obtained from light petroleum distillates by means of a selective solvent treatment. The extract is passed with free hydrogen over suitable catalysts under pressures in excess of at mospheres and preferably between 50 to 200 atmospheres, and at temperatures above about 900 F. and preferably within the range of 930 to 1,050 F. The amount of the hydrogen is about 45 1,000 to 4,000 cubic feet per barrel of extract fed. The catalysts used may be oxides or sulfides of the metals of the 6th group of elements with suitable promotors, such as, alkali or alkali earth oxides. A fraction of the hydrogenated oiq'oduct boiling between 200 and 450 F. is prefbly used for the purposes of the present proc- The hydrogenated solvents are especially ed for use as diluents or oil solvents in deprocesses because they have a high soluoil at lowtemperatures, a low solubility for wax, and are stable, i. e. do not react with oil or wax to form objectionable compounds, and do not decompose while separated from the oil by means of distillation. The solvent mixture may consist of approximately 20 to of wax precipitant and to 40% of hydrogenated solvent. The percentages will depend on the wax precipitant and also on the raw material to be dewaxed, less precipitant being used for the dewaxing of heavy cylinder stocks than for light paraffin distillates. Higher dewaxing temperatures require more precipitant. Usually two volumes of the dewaxing mixture to one volume of the oil give good results, although a higher ratio of the dewaxing mixture gives higher throughputs and better yields and will allow the admixture of more precipitant.

The oil to be dewaxed and the dewaxing mixture are thoroughly admixed with each other at temperatures of say to F. or above the pour point of the waxy oil and then cooled to a temperature at which the wax precipitates out. The dewaxing temperature depends on the desired pour point of the dewaxed oil and is somewhat, say about 10 F., below the pour point. The precipitated wax may be separated from the oilsolvent mixture by various methods known in the art, such as cold settling, filter pressing, centrifuging, etc. The dewaxing mixture is then removed from the dewaxed oil by means of distillation or by any other means.

' Referring now to the drawing, the same will be described in conjunction with the method of operating the apparatus. The wax-containing feed stock from storage tank I, which is preferably mildly heated, is mixed with the dewaxing mixture from tank 2 in the heated mixing chamber 3 and passed through a series of heat exchangers represented by 4, 5 and 0, in which it is partially cooled by the outgoing cold dewaxed solution. These exchangers should preferably be of the type which have wax scrapers for keeping the wax from congealing on the cooling surface. The partially chilled solution then passes to the ammonia chillers 1 and}, where it is further chilled to a point slightly below the pressing temperature, e. g., 0 F. or lower. The chillers are also provided with wax scrapers. The chilled solution is then pumped to a surge tank 9 from which the filters 10, II and I2 are fed by means of pump I3 under pressure of about 50 lbs. per square inch. When a suitable wax cake has been built up the feed is shut off and the dewaxing mixture from tank 2 is admitted, after it has been chilled in the ammonia chiller M, to wash the wax cake free of oil. The cold dewaxed solution and washed solvent pass from the filters to the heat exchangers 4, 5 and 6, flowing countercurrent to the incoming waxy solution. The dewaxed solution from chiller 4 is then passed to the fired heating coil l5 and then flashed into a fractionating tower Hi, from which the solvent is taken overhead, condensed in condenser l1 and returned to the storage tank 2. the bottom of the tower goes to the dewaxed oil storage tank I8. The wax cake isdumped from the presses I0, I! and i2, is passed through the fired heating coil l9, then flashed into the fractionating tower 20, from which the solvent is taken overhead, condensed in condenser 2|, returned to the storage tank 2 and the stripped wax withdrawn from the bottom to a storage tank (not shown).

The following examples will illustrate my invention:

A waxy cylinder stock from Ranger crude of 140 seconds Saybolt viscosity at 210 F. is diluted with two volumes of a dewaxing mixture comprising of hydroformed solvent and 20% of isopropyl alcohol. The mixture is heated to 110 F. approximately, then admixed with lb. of diatomaceous earth known under the trade mark Filter Cel per gallon of waxy feed stock, chilled with agitation at the rate of 5 F. per hour to 0 F. and the slurry pressed on a Vallez filter press under 50 lbs. per square inch pressure. A throughput equivalent to about 330 barrels per day per 720 square feet of pressing surface is obtained and the pour point on the stripped dewaxed oil is 20 F.

As another example, a lubricating oil fraction from Reagan crude of 'seconds Saybolt viscosity at 210 F. containing both crystalline and amorphous waxes is diluted with two volumes of a dewaxing mixture containing 65% of hydrogenated solvent with a boiling range of 297 F. to 408 F. produced by the vapor phase hydrogenation of a liquid S02 extract from a refined oil, and 35% of acetone. This mixture is heated to F. to insure complete solution of all waxes, chilled to 0 F. with agitation, and the slurry pressed on a Vallez filter under 50 lbs. pressure. The mixture of the waxes, which, of course, cannot be handled either by current pressing or centrifuging methods, is pressed readily from this mixed solvent with a throughput'equivalent to about 300 barrels per day per 720 square feet of filter press surface, giving a yield of approximately 90% of dewaxed oil of 20 F. pour point. The wax cake is washed with additional solvent, approximately 1 volumes of solvent per volume of waxy charge, and gives a relatively oil-free wax. In both cases the mixed solvents are recovered from the dewaxed solution and the wax cakes by distillation.

The stripped dewaxed oil from The process may be modified in various ways; thus, for example, two or more wax precipitants may be used in the dewaxing mixture. Other oil-solvents may be used in conjunction with the hydrogenated solvents. As examples of other oil-solvents we may cite benzene, toluene, petroleum naphtha, etc.

The invention is not to be limited by the examples given for illustration but only by the following claims in which it is my intention to claim all novelty inherent in the invention.

What I claim is:

1. A process for dewaxing Wax-containing oil which comprises diluting the oil with a solvent comprising a hydrogenated solvent obtained by subjecting a petroleum distillate of the type of kerosene and gas oil to the action of hydrogen in vapor phase under pressure in excess of 20 atmospheres, at a temperature between 900 and 1,050 F., using between 1,000 and 4,000 cu. ft.

of hydrogen/barrel of oil, chilling the mixture of oil and solvent to a temperature at which wax is caused to precipitate, removing the precipitated wax and recovering the dewaxed oil.

2. A process according to claim 1 in which the solvent comprises a hydrogenated solvent obtained by the vapor phase destructive hydrogenation of an extract obtained by treating a low boiling petroleum distillate with a selective solvent of the type which has preferential solvent power for aromatic and naphthenic hydrocarbons.

3. A process for dewaxing a wax-containing oil which comprises diluting the oil with a mixture comprising a wax precipitant and a hydrogenated solvent obtained by subjecting an extract obtained by the selective solvent treatment of a low boiling petroleum distillate to the action of hydrogen in vapor phase under pressure in excess of 20 atmospheres, at a temperature between 900 and 1,050 F., using between 1,000 and 4,000 cu. ft. of hydrogen/barrel of oil, chilling the mixture of oil and diluent to a temperature at which wax is caused to precipitate, removing the wax and recovering the dewaxed oil.

4. A process according to claim 3 in which the hydrogenated solvent consists of a fraction boiling between 200 and 450 F. obtained by the vapor phase destructive hydrogenation of an extract obtained in the treatment of a low boiling petroleum distillate with a selective solvent having preferential solvent power for aromatic and naphthenic hydrocarbons.

5. A process according to claim 3 in which the wax precipitant consists of acetone.

6. A process according to claim 3 in which the wax precipitant consists of isopropyl alcohol.

JOHN V. STARR. 

